Surface Energy Properties of Polylactic Acid Treated with a Gamma Radiation Dose Used for Sterilization

The effect of γ-irradiation on polylactic acid samples obtained by injection molding has been studied depending on the dose in the range of 10−100 kGy. Determination of the surface energy characteristics of polylactic acid (surface free energy and its components, as well as surface polarity) has shown that with an increase in the radiation dose, all parameters first decrease to a minimum value and then begin to increase. Obviously, processes of carbonization and radiation-induced oxidation caused by crosslinking and degradation, respectively, occur in the surface layer. According to the differential thermal and thermogravimetric analysis data, the determined physical and mechanical characteristics, and the melt flow index, competing radiation-chemical processes of crosslinking and degradation take place in polylactic acid, with the latter process prevailing with increasing radiation dose.